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Graphite-based metal transition-layer substrates hold great potential for preparing large-area diamond films and achieving crack-free release. In this study, a five-inch crack-free free-standing diamond film was prepared on a graphite substrate with a sacrificial Mo/Ti double-layer transition layer using direct-current arc plasma jet chemical vapor deposition (DC jet CVD). The interfacial bonding and diffusion behavior between the diamond and the transition layers were investigated. The effect of abundant metal particles and elemental diffusion between layers on film adhesion and stress release are discussed and analyzed. The surface of Ti layer prepared by the multi-arc ion-plating contains numerous metal particles that provide a template for the fine-crystalline Mo layer. Metal particles are encapsulated and embedded in the diamond and act as anchors that ensure the stability of the substrate–diamond bond during high-temperature deposition. After deposition, those metal particles act as weak points and play crucial stress-release roles. Mutual elemental diffusion occurs between the Ti, Mo, and diamond layers. Ti penetrates the Mo layer to form a continuous 140-nm-thick thin layer during the initial deposition period, facilitating diamond nucleation. Carbon from the plasma and diamond diffuses into the metal transition layer. Thermal stress generated between the diamond and the graphite substrate is released by destroying the metal transition layer with high thermal expansion coefficient and low elastic modulus during cooling from the deposition temperature. Cracks rapidly propagate along the interface between destroyable transition layers and graphite substrate, which results in the liftoff of a fully crack-free diamond film. [Display omitted] [ABSTRACT FROM AUTHOR]

High-quality nanodiamond coatings have immense potential in cutting tools, electronic devices, and biomedicine. Introducing Ar is a crucial method of enhancing the quality of these films. This study examines the influence of Ar on the spatial distribution of CH 4 /H 2 microwave plasma parameters, group density, and the subsequent deposition of nanodiamond coatings. The electron number density, discharge volume, gas temperature and molecular mean free path increase with the increase of Ar volume fraction. In addition, the dissociation rate of H 2 increases with the increase of Ar volume fraction, which leads to more H. For the Ar-rich deposition atmosphere, the hydrocracking rate of CH 4 reduces and the hydrocracking rate of C 2 H increases, resulting in a decline in the number density of CH 3 and an increase in the amount of C 2 at the core of the discharge region. C 2 H 2 is the primary neutral hydrocarbon in the discharge, while CH 3 is the leading neutral single‑carbon hydrocarbon. The total flux of atomic hydrogen and C 2 increases with Ar, which is a key factor in improving the quality of nanocrystalline diamond crystals and enhancing renucleation. The optical emission spectroscopy of CH 4 /H 2 /Ar plasma analysis indicates an accelerated generation rate of H and C 2 with an increase in Ar volume fraction. The deposition experiments demonstrate that an increase in Ar volume fraction results in a reduction in the size of diamond grains, an augmentation in the coating coverage on the substrate surface, and an acceleration in the coating deposition rate. Meanwhile, the quality of diamond crystal is almost unaffected. • Self-consistent multiphysics modeling of microwave plasma of CH 4 /H 2 /Ar gas mixture. • Kinetics of chemical reaction in microwave plasma of CH 4 /H 2 /Ar-rich gas mixture. • Nanocrystalline diamond films with higher surface coverage, faster growth rate and finer grains were prepared by adding Ar. • The average grain size of nanocrystalline diamond coating is a linear function of the total flux of C 2 species. • The growth rate was positively correlated with substrate temperature, rather than total species flux. [ABSTRACT FROM AUTHOR]